ABSTRACT This paper is concerned with the torque distribution problem including slip limitation and actuator fault tolerance to improve vehicle lateral stability and maneuverability of six- wheeled skid-steered vehicles. The torque distribution algorithm to distribute wheel torque to each wheel of a skid- steered vehicle consists of an upper level control layer, a lower level control layer and an estimation layer. The upper level control layer is designed to obtain longitudinal net force and desired yaw moment, while the lower level control layer determines distributed driving and braking torques to six wheels. The algorithm takes vehicle speed, slip ratio and tire load information from the estimation layer, as well as actuator fault information from each in-wheel motor controller unit. Wheel torque command to each wheel is determined to minimize allocation error for longitudinal net force and desired yaw moment, to keep wheel slip ratio below the limit value, and also to tolerate a failure of an in- wheel motor. The maneuvering performance of the six- wheeled and skid-steered vehicle with the proposed driving controller for both on-road and off-road conditions has been compared with a conventional vehicle via computer simulations. INTRODUCTION The six-wheeled skid-steered vehicle is being developed to military purpose with the wide range of applications such as logistics supports, surveillance and light combat operation. Unlike the conventional Ackerman-steered wheeled vehicles, the skid-steered vehicle system is not equipped with steeringlinkages. Instead, it is steered through differential traction force which is created from in-wheel motor at each wheel. On the other hand, maneuverability on off-road surfaces for skid- steered vehicle is better and the volume in the front hull is almost the same as the rear hull. However, skid steering reduces considerable life cycle of pneumatics particularly on road and it shows quite poor driverability at high speed. Also it needs more power than Ackerman steering. In this research, torque distribution problem including slip limitation, actuator fault tolerance and estimation problem is presented to improve vehicle stability and maneuverability of six-wheeled skid-steered vehicles. Many skid-steering control methods have been studied and actively developed to improve maneuverability of the skid-steered vehicle. S.Golconda presented the steering controller of a six-wheeled vehicle based on skid steering[1]. The steering controller consists of a PID controller with two filters, a prediction filter and a safely filter. J.T. Economou, R.E. Colyer proposed fuzzy logic control of wheeled skid-steer electric vehicles[2]. W. E. Dixon, et al., were investigated nonlinear control of wheeled mobile robots[3]. Recently, J. Kang, et al., have been designed a driving control algorithm based on skid steering for a Robotic Vehicle with Articulated Suspension (RVAS). [4] They designed a controller to optimize longitudinal tire forces and to keep a slip ratio below a limit value as well as to track the desired longitudinal tire force. However, their optimal tire force distribution strategy considered a magnitude vertical tire force and wheel slip control only and those two factors could not be treated conjunctly. And also, vehicle speed estimation problem was not mentioned though Torque Distribution Algorithm of Six-Wheeled Skid- Steered Vehicles for On-Road and Off-Road Maneuverability2013-01-0628 Published 04/08/2013 Jaewon Nah and Kyongsu Yi Seoul National Univ Wongun Kim and Yeogiel Yoon Samsung Techwin Copyright © 2013 SAE International doi:10.4271/2013-01-0628Downloaded from SAE International by Univ of California Berkeley, Wednesday, August 01, 2018tire force distribution strategy needs vehicle speed information. In this paper, a vehicle dynamic model using “TruckSim” is described in the second section. The proposed driving control algorithm and the simulation results are described in th